Ragbaby

History

The Ragbaby cipher was invented by the American Cryptogram Association (ACA) member SHERLAC and was first described in the Jul-Aug 1955 edition of the ACA's magazine The Cryptogram.

Description

Plaintext letters are located in a keyed alphabet and a numerical key determines the offset from this to form the cipher letter. The numerical key is based on the word number in the plaintext and the position in the word. As first described the keyed alphabet uses a 24-letter alphabet with I/J and W/X combined though a 26- and 36-letter alphabet could be used. The keyed alphabet is created from a keyword, with repeated letters being omitted, followed by the unused letters of the alphabet in alphabetic order. J and X are replaced by I and W respectively. The plaintext is written retaining word divisions and below each word numbers are written in consecutive order starting with 1 under the first word, 2 under the second, 3 under the third and so on. Then the letters in each are number consecutively starting at the word number. Numbers start again at 1 if it exceeds the number of letters in the alphabet. Words containing hyphens and apostrophes are treated as a single word.

W e l l d o n e i s b e t t e r t h a n w e l l s a i d

1 2 3 4 2 3 4 5 3 4 4 5 6 7 8 9 5 6 7 8 6 7 8 9 7 8 9 10

Next the keyed alphabet is created. Using the keyword FRANKLIN it's reduced to FRANKLI when repeated letters are removed. Appending unused alphabet letters produces the keyed alphabet:

FRANKLIBCDEGHMOPQSTUVWYZ

To encipher the text the plaintext letter is found in the keyed alphabet. Count forward in the alphabet by the number below the plaintext letter to locate the ciphertext letter. For example below plaintext letter W is the number 1. Counting 1 place from W in the alphabet gives Y. Then 2 places from E is H, 3 places from L is C and so on. If the end of the alphabet is reached start again from the beginning.

Example

Keyword: FRANKLIN

Plaintext: Well done is better than well said.

Plaintext: Well done is better than well said

Number key: 1234 2345 34 456789 5678 6789 78910

Ciphertext: YHCD GSBP DW GPFRTE ZTDG NSMO FEPU

Solving

Solving methods: Hill Climbing and Dictionary keyword search.